The present invention generally relates to the use of polyamine polyoxides as asphalt emulsifiers. More particularly, the invention concerns an improved process for stabilizing an asphalt in water emulsion using a di-tertiary amine dioxide as an asphalt emulsifier.
Asphalt in water emulsions are used for road construction and repair, as well as in the construction industry as coatings and sealers. The asphalt properties are obtained after the emulsions set or cure, when the droplets of asphalt coalesce and adhere to the substrate and water is removed.
The rate of this setting process depends on the reactivity of the emulsion and the reactivity of the substrate. Emulsions are classified as rapid, medium and slow-setting types depending on their reactivity. Slow-setting emulsions find use in applications, such as cold mix, where the emulsion is mixed with aggregate and the mixture is used to pave a roadway.
Emulsions can be classified into cationic (positive) or anionic (negative) types depending on the charge on the asphalt droplets. Cationic emulsions are used for siliceous aggregates, like quartz, since such aggregates have negatively charged surfaces. The cured film from cationic emulsions generally adheres much better to siliceous aggregates than does the cured film from anionic emulsions. Generally, different emulsifiers are used for cationic emulsions than are used for anionic emulsions.
Nonionic emulsifiers, such as ethoxylated nonylphenols, can be used as part of an emulsifier or alone in both cationic and anionic slow-setting emulsions. However, at use levels comparable to the inventive emulsifier, the anionic and cationic slow-setting emulsions of ethoxylated nonylphenols are deficient in quality. Additionally, films of asphalt derived from such emulsions tend to strip off the aggregate when soaked in water.
Amine monoxides, such as RN(CH3)2O, RCONCH2CH2CH2N(CH3)2O(an amide amine oxide) or RN(CH2CH2OH)2O, where R is a C12 alkyl, coconut oil or tallow, have some efficacy as cationic asphalt emulsifiers. However, they generally cannot be used to produce both anionic and cationic emulsions. When they can form both anionic and cationic emulsions, the quality of the emulsions is deficient and they do not meet the requirements of slow-setting emulsions at economic use levels. Instead, they form rapid- or medium-setting emulsions which cannot be used with reactive aggregates.
The use of amine oxides as asphalt emulsifiers has been disclosed. For example, DE 1 719 449 (DE""449) discloses the use of tertiary amine oxides as a bitumen emulsion additive which is combined with a cationic emulsifier for road surfacing, while WO 94/03560 discloses the use of amine oxides as a cationic surfactant in asphalt/bitumen emulsions. Additionally, EP 0 037 996 discloses the use of an amine oxide with a napthenoyl group for emulsifying bituminous products. These amide amine oxides would have the same problems as the amine oxides discussed above.
A di-tert-amine dioxide comprising (hydrogenated) tallow groups is disclosed for use as a detergent or as an emulsifier of, for example, long chain fatty amines used as corrosion inhibitors in steam condensate lines, according to GB 1 104 491. However, there is no disclosure or suggestion of its use as an asphalt emulsifier.
The asphalt residues (i.e. after curing of the emulsion) from slow-setting asphalt emulsions, especially slow-setting anionic emulsions, show poor adhesion to aggregates such as quartzite. The result is poor durability of road materials prepared using these emulsions.
The asphalt residues from slow-setting emulsions prepared from the polyamine polyoxide emulsifiers of the invention, however, show good adhesion and have particularly better adhesion than the residues derived from slow-setting cationic, anionic or nonionic emulsions prepared with the commonly-used nonylphenolethoxylate emulsifiers.
The present invention generally relates to a method of emulsifying asphalt using a novel asphalt emulsifier, an asphalt emulsion containing the novel asphalt emulsifier, and a cold mix of the asphalt emulsion containing the novel asphalt emulsifier. The method emulsifies a mixture of asphalt and water by adding an emulsifying effective amount of a novel asphalt emulsifier of at least one polyamine polyoxide. A polyamine (or polytertiaryamine) is defined herein as having more than one amine group, such as a di-, tri- or tetra-amine, etc. A polyoxide is defined herein as having more than one oxide group, such as a di-, tri- or tetra-oxide, etc.
The invention is especially useful in slow setting emulsions, since lower use levels are required when using the inventive emulsifier and the emulsifier can be used for either anionic or cationic slow setting emulsions depending on whether art acid or alkaline water phase is used. Both the cationic and anionic slow setting asphalt emulsions are of good quality and meet the requirements of slow setting grades at low use levels. The cured asphalt residue from emulsions made with the inventive emulsifier adhere better to aggregates than the asphalt residue from emulsions prepared with nonionic nonylphenolethoxylate emulsifiers.
Further, the emulsions of the present invention can be used for cold mix, where they exhibit advantages compared with a conventional cationic mixing grade emulsifier. Additionally, the inventive asphalt emulsifiers are compatible with both cationic and anionic co-emulsifiers, especially when combined with co-emulsifiers conventionally used for medium and rapid-setting emulsions. It is, thus, very economical to use the inventive asphalt emulsifiers, since lower use levels are required and it is only necessary to stock a single emulsifier for both anionic and cationic emulsions and for slow setting emulsions.
These and other objects of the invention are readily apparent from the following disclosure.